Synthesis and Characterization of Metal Organic Frameworks for Hydrogen Storage

• Main Authors: Abhijit Krishna Adhikari, 歐里
• Other Authors: Kuen-Song Lin
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/49541964720321230958

碩士 === 元智大學 === 化學工程與材料科學學系 === 97 === Hydrogen is a clean power source, it provides energy without producing any pollutions. For the utilization of hydrogen, hydrogen storage technology is quite important. Recently, microporous metal-organic frameworks (MOFs), the crystalline compounds, so called inorganic-organic covalent compound has shown highly porous frameworks held together by strong metal–oxygen–carbon bonds and with exceptionally large surface area, thermal stability, and high capacity for hydrogen storage. Furthermore, the hydrogen uptake is correlated with the specific surface area for crystalline microporous materials. On the other hand, initiated by climate change concerns and the need to reduce CO2 (greenhouse gas) emissions by the power industries. CO2 capture and storage is very important issue due to environment safety. Recently, MOFs showed their good adsorption capacity for CO2 also. The adsorption capacity greatly depends on the surface area, the interactions between adsorbed molecule and the metal clusters of the MOFs. Therefore, the main objective of the present study is to develop new synthetic routes for MOFs as hydrogen storage materials. The fine structural characterization of MOFs has been performed by XRD, FE-SEM, TEM, BET, TGA, ESCA, EPR and XANES/EXAFS technique. Experimentally, MOFs were synthesized with different metal clusters combined with different organic linkers into different solvents. The particle size of these MOFs named MIL-47, MIL-100, MIL-101, MIL-102 (MIL stands for Material of the Lavoisier Institute) and MOF-177 were 2~15, 1~3, 1~5, 10~15 and 2~5 μm, respectively revealed by FE-SEM micrographs. Since as-synthesized MOFs contain many impurities that may cause low porosity, to improve the specific surface area and porosity the samples were calcined at high temperature. The MOFs were thermally well stable around 275~400oC than other organic compounds. XANES/EXAFS spectroscopy was performed to identify the fine structures of MOFs. The XANES spectra indicated that the valency of Vanadium ion in MIL-47 was VIII, and the valency of chromium was CrIII in MIL-100, MIL-101 and MIL-102. The EXAFS data also revealed that MIL-47 had first shell of V−O bonding with 1.8467 and 1.9761 Å and MIL-100, MIL-101 and MIL-102 had Cr−O first shell with 2.1949, 2.1934 and 2.1956 Å respectively.